1996 corolla ac problem compesser not engaging?

Hi,
My better half just bought a '96 corolla from original owner w/ 85,000 k.
anyways the owner stated the ac always worked ,but when we checked out the car, the compresser clutch would not turn over/engage when the ac fuction was on and or defroster.
clutch does spin free and fuses are ok.
Its winter but the comp. clutch should kick in with deforst or ac mode correct?
there are ac releys but I haven't purschased a manual for her car yet [I need to repalce the timing belt also as car still has original] and don't know if they would cause this or a low 134 level?
She still purschaed the car as it was super clean.
any thoughts relay,, low 134??
thanks,
Brett